OPTICAL-MODEL ANALYSIS OF PARITY-NONCONSERVING NEUTRON-SCATTERING AT EPITHERMAL ENERGIES

The parity nonconserving (PNC) resonant scattering of neutrons at epithermal energies is discussed within the optical model. We show that the empirical optical-model potential with real PNC interaction does not account for the appreciable resonance-averaged difference between positive and negative helicity total p-neutron cross sections [Delta sigma] for Th-232, but reproduces the very small [Delta sigma] for U-238. It is suggested that the 2p-1h local doorway, previously proposed to; account for the sign correlation in Th-232, is the main source for the large [Delta sigma] seen in this system. It is further proposed that if an optical potential is used to account for [Delta sigma], a complex PNC interaction is required in cases involving strong sign correlation.